JP2010048108A - Internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cylinder injection type internal combustion engine reducing oil dilution and a PM generating amount during idling after engine startup. <P>SOLUTION: In the cylinder injection type internal combustion engine, an ECU 51 determines whether oil dilution suppressing control is required on the basis of an detected or estimated oil dilution ratio and oil temperature detected by an oil temperature sensor 63 during warming up after engine startup, and executes the oil dilution suppressing control when oil dilution suppressing control is determined to be required. Timing for closing an exhaust valve 22 by an exhaust variable valve mechanism 28 is taken as the middle time of the intake stroke. A part or the whole of the required fuel injection amount is injected to an injector 41 until the exhaust valve 22 is closed from the early stage of the intake stroke. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an internal combustion engine, and more particularly to an in-cylinder direct injection internal combustion engine that directly injects fuel into a combustion chamber.

  2. Description of the Related Art Conventionally, an in-cylinder injection internal combustion engine is known in which fuel spray is directly injected into a combustion chamber in an intake stroke or compression stroke, and an air-fuel mixture of fuel spray and air is spark-ignited by an ignition plug. Such an in-cylinder injection internal combustion engine is characterized in that the injected fuel spray is more likely to adhere to the cylinder inner wall than an internal combustion engine that injects fuel spray into the intake passage. For this reason, in a cold state where the engine temperature is low, vaporization of fuel spray adhering to the inner wall of the cylinder (hereinafter referred to as “adhered fuel”) is not promoted, and the adhering fuel may remain even at the ignition timing. In this case, the attached fuel may be discharged into the atmosphere without being burned, or the attached fuel may be mixed into the oil and cause oil dilution.

  For example, Patent Document 1 discloses a technique for suppressing oil dilution by fuel in a direct injection internal combustion engine by setting the fuel injection timing to a timing at which the fuel does not adhere to the cylinder liner.

  However, it is possible to suppress oil dilution by suppressing the fuel injection timing. However, if the fuel injection timing is set to the initial stage of the intake stroke, fuel adheres to the piston crown surface, which may cause smoke and PM generation. There is a problem of becoming.

JP 2002-13428 A

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a direct injection internal combustion engine capable of reducing oil dilution and PM generation during warm-up after starting the engine. .

  In order to solve the above-described problems and achieve the object, the present invention provides a variable valve mechanism capable of changing at least the opening / closing timing of an exhaust valve in an internal combustion engine in which fuel is directly injected into a cylinder by a fuel injection device, An oil dilution rate calculating means for detecting or estimating the oil dilution rate of the engine oil, an oil temperature calculating means for detecting or estimating the oil temperature of the engine oil, and the oil dilution rate calculating means during the warm-up operation after starting the engine. Based on the detected or estimated oil dilution rate and the oil temperature detected or estimated by the oil temperature calculating means, a determination means for determining whether or not oil dilution suppression control is necessary, and the determination means requires oil dilution suppression control Control means for executing the oil dilution suppression control when it is determined that, in the oil dilution suppression control, the exhaust valve of the variable valve mechanism Close timing to the intake stroke mid-between from the beginning of the intake stroke until closing the exhaust valve, and wherein the ejecting part or all of the required fuel injection amount to the fuel injection device.

  According to a preferred aspect of the present invention, in the oil dilution suppression control, it is desirable that the fuel is dividedly injected and the fuel is injected twice during the intake stroke until the exhaust valve is closed.

  Further, according to a preferred aspect of the present invention, X (%) of the required fuel injection amount is injected in the second fuel injection, and 100-X (%) of the required fuel injection amount is injected in the first fuel injection. It is desirable to increase the X (%) as the oil dilution ratio increases.

  According to a preferred aspect of the present invention, in the oil dilution suppression control, it is desirable to retard the closing timing of the exhaust valve as the oil dilution ratio increases.

  According to the internal combustion engine of the present invention, in an internal combustion engine in which fuel is directly injected into a cylinder by a fuel injection device, a variable valve mechanism that can change at least the opening / closing timing of an exhaust valve, and an oil dilution rate of engine oil are detected. Or an oil dilution rate calculating means for estimating, an oil temperature calculating means for detecting or estimating the oil temperature of the engine oil, and an oil dilution rate detected or estimated by the oil dilution rate calculating means during a warm-up operation after starting the engine and Based on the oil temperature detected or estimated by the oil temperature calculation means, a determination means for determining whether or not oil dilution suppression control is necessary, and when the determination means determines that oil dilution suppression control is necessary, Control means for executing oil dilution suppression control, and in the oil dilution suppression control, the closing timing of the exhaust valve of the variable valve mechanism is set to the intake line. In the middle period, part or all of the required fuel injection amount is injected into the fuel injection device from the beginning of the intake stroke until the exhaust valve is closed. There is an effect that it becomes possible to provide an internal combustion engine capable of reducing the PM generation amount.

  Embodiments of an internal combustion engine according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. In addition, constituent elements in the following embodiments include those that can be easily replaced by those skilled in the art or those that are substantially the same.

  FIG. 1 is a schematic configuration diagram showing an engine according to an embodiment of the present invention. An engine 10 as an internal combustion engine according to this embodiment is mounted on a vehicle such as a passenger car or a truck as shown in FIG. 1, and a multi-cylinder in-cylinder injection in which fuel spray is directly injected into a combustion chamber 18 by an injector 41 described later. This is a so-called four-cycle engine that performs a series of four strokes consisting of an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke while a piston 14 provided in a cylinder bore 13 so as to be capable of reciprocating is reciprocated twice. is there.

  The engine 10 is a multi-cylinder in-cylinder injection type, and a cylinder head 12 is fastened on a cylinder block 11. A plurality of cylinder bores 13 formed in the cylinder block 11 can move pistons 14 up and down. It is mated. A crankcase 15 is fastened to the lower part of the cylinder block 11, and a crankshaft 16 is rotatably supported in the crankcase 15. Each piston 14 is connected to the crankshaft 16 via a connecting rod 17. Has been. An oil pan 62 for storing engine oil supplied to each part of the engine 10 is provided at the bottom of the crankcase 15. The oil pan 62 is provided with an oil temperature sensor 63 that detects the oil temperature of the engine oil, and outputs the detected oil temperature to the ECU 51. Although the oil temperature is detected by the oil temperature sensor 63 here, it may be estimated based on the engine coolant temperature, the operating state, or the like.

  The combustion chamber 18 is constituted by a wall surface of the cylinder bore 13 in the cylinder block 11, an in-cylinder ceiling as a lower surface of the cylinder head 12, and a top surface of the piston 14, and the combustion chamber 18 is an upper portion, that is, the cylinder head 12. The pent roof shape which inclines so that the center part of the in-cylinder ceiling part as a lower surface of this may become high is comprised. In the combustion chamber 18, a mixture of fuel and air can be combusted, and an intake port 19 and an exhaust port 20 are formed to face each other on an in-cylinder ceiling that is an upper portion of the combustion chamber 18. 19 and the exhaust port 20, the lower end portions of the intake valve 21 and the exhaust valve 22 are located, respectively. The intake valve 21 and the exhaust valve 22 are supported by the cylinder head 12 so as to be movable in the axial direction, and are urged and supported in a direction (upward in FIG. 1) for closing the intake port 19 and the exhaust port 20. ing. An intake camshaft 23 and an exhaust camshaft 24 are rotatably supported on the cylinder head 12, and the intake cam 25 and the exhaust cam 26 are in contact with upper ends of the intake valve 21 and the exhaust valve 22.

  Although not shown, the crankshaft sprocket fixed to the crankshaft 16 and the camshaft sprockets respectively fixed to the intake camshaft 23 and the exhaust camshaft 24 are wound with endless timing chains. The crankshaft 16, the intake camshaft 23, and the exhaust camshaft 24 can be interlocked.

  Therefore, when the intake camshaft 23 and the exhaust camshaft 24 rotate in synchronization with the crankshaft 16, the intake cam 25 and the exhaust cam 26 move up and down the intake valve 21 and the exhaust valve 22 at a predetermined timing. 19 and the exhaust port 20 can be opened and closed so that the intake port 19 and the combustion chamber 18 can communicate with the combustion chamber 18 and the exhaust port 20, respectively. In this case, the intake camshaft 23 and the exhaust camshaft 24 are set to rotate once (360 degrees) while the crankshaft 16 rotates twice (720 degrees). Therefore, the engine 10 executes the four strokes of the intake stroke, the compression stroke, the expansion stroke, and the exhaust stroke while the crankshaft 16 rotates twice. At this time, the intake camshaft 23 and the exhaust camshaft 24 are set to one. It will rotate.

  The valve mechanism of the engine 10 is a variable valve timing mechanism (VVT) 27, 28 that controls the intake valve 21 and the exhaust valve 22 at an optimal opening / closing timing according to the operating state. It has become. The intake / exhaust variable valve mechanisms 27, 28 as variable valve means are configured by providing VVT controllers 29, 30 at the shaft ends of the intake camshaft 23 and the exhaust camshaft 24. 32, the phase of the camshafts 23 and 24 with respect to the cam sprocket is changed by causing the hydraulic pressure from 32 to act on an advance chamber and a retard chamber (not shown) of the VVT controllers 29 and 30, and the opening / closing timing of the intake valve 21 and the exhaust valve 22 is changed. Can be advanced or retarded. In this case, the intake / exhaust variable valve mechanisms 27, 28 advance or retard the opening / closing timing with the operating angle (opening period) of the intake valve 21 and the exhaust valve 22 being constant. In addition, the intake camshaft 23 and the exhaust camshaft 24 are provided with cam position sensors 33 and 34 for detecting the rotational phase thereof.

  A surge tank 36 is connected to the intake port 19 via an intake manifold 35, and an intake pipe 37 is connected to the surge tank 36. An air cleaner 38 is attached to an air intake port of the intake pipe 37. . An electronic throttle device 40 as a load adjusting means having a throttle valve 39 is provided downstream of the air cleaner 38 in the air flow direction. Further, the cylinder head 12 is provided with an injector (fuel injection valve) 41 as fuel injection means for directly injecting fuel into the combustion chamber 18. The injector 41 is located on the intake port 19 side and is inclined at a predetermined angle in the vertical direction. The injector 41 is capable of injecting fuel toward the top surface of the piston 14 so that the fuel gets on the intake air flow generated in the combustion chamber 18. An injector 41 attached to each cylinder is connected to a delivery pipe 42, and a high pressure fuel pump (fuel pump) 44 is connected to the delivery pipe 42 via a high pressure fuel supply pipe 43. Further, the cylinder head 12 is provided with a spark plug 45 that is located above the combustion chamber 18 and ignites the air-fuel mixture.

  On the other hand, an exhaust pipe 47 is connected to the exhaust port 20 via an exhaust manifold 46. The exhaust pipe 47 is a three-way element that purifies harmful substances such as HC, CO, and NOx contained in the exhaust gas. Catalysts 48 and 49 are mounted. Further, the engine 10 is provided with a starter motor 50 that performs cranking. When an unillustrated pinion gear meshes with the ring gear when the engine is started, the rotational force is transmitted from the pinion gear to the ring gear to rotate the crankshaft 16. Can do.

  By the way, the vehicle is equipped with an electronic control unit (ECU) 51 that is configured around a microcomputer and can control each part of the engine 10, and the ECU 51 can control the injector 41, the spark plug 45, and the like. Yes. That is, an air flow sensor 52 and an intake air temperature sensor 53 are mounted on the upstream side of the air flow direction of the intake pipe 37, and an intake pressure sensor 54 is provided in the surge tank 36, and the measured intake air amount and intake air temperature are measured. The intake pressure (intake pipe negative pressure) is output to the ECU 51. In addition, a throttle position sensor 55 is attached to the electronic throttle device 40, and the current throttle opening is output to the ECU 51. Here, the ECU 51 can calculate the engine load (load factor) as the internal combustion engine load based on the detected throttle opening and intake air amount. The accelerator position sensor 56 outputs the current accelerator opening to the ECU 51. Further, a crank angle sensor 57 as a crank angle detecting means for detecting the crank angle of the engine 10 outputs the detected crank angle of each cylinder to the ECU 51, and the ECU 51 performs an intake stroke in each cylinder based on the detected crank angle. In addition to determining the compression stroke, the expansion stroke, and the exhaust stroke, the engine speed is calculated. Here, the engine speed corresponds to the rotational speed of the crankshaft 16 in other words. If the rotational speed of the crankshaft 16 increases, the rotational speed of the crankshaft 16, that is, the engine rotational speed of the engine 10 also increases. Get higher.

  The cylinder block 11 is provided with a water temperature sensor 58 that detects the engine cooling water temperature, and outputs the detected engine cooling water temperature to the ECU 51. The delivery pipe 42 communicating with each injector 41 is provided with a fuel pressure sensor 59 that detects the fuel pressure, and outputs the detected fuel pressure to the ECU 51. On the other hand, the exhaust pipe 47 is provided with an A / F sensor 60 that detects the air-fuel ratio of the engine 10 upstream of the three-way catalyst 48 in the exhaust gas flow direction, and an oxygen sensor 61 downstream of the exhaust gas flow direction. The A / F sensor 60 detects the exhaust gas air-fuel ratio of the exhaust gas before being introduced into the three-way catalyst 48, outputs the detected air-fuel ratio to the ECU 51, and the oxygen sensor 61 is discharged from the three-way catalyst 48. Thereafter, the oxygen concentration of the exhaust gas is detected, and the detected oxygen concentration is output to the ECU 51. The air-fuel ratio (estimated air-fuel ratio) detected by the A / F sensor 60 is used for feedback control of the air-fuel ratio (theoretical air-fuel ratio) of the mixed gas composed of intake air and fuel. That is, the A / F sensor 60 detects the exhaust air-fuel ratio from the rich range to the lean range from the oxygen concentration in the exhaust gas and the unburned gas concentration, and feeds this back to the ECU 51 to correct the fuel injection amount. Thus, the combustion can be controlled to an optimum combustion state that matches the operating state.

  Therefore, the ECU 51 drives the high-pressure fuel pump 44 based on the detected fuel pressure so that the fuel pressure becomes a predetermined pressure, and also detects the detected intake air amount, intake air temperature, intake pressure, throttle opening, accelerator opening. The fuel injection amount (fuel injection period), the injection timing, the ignition timing, etc. are determined based on the engine operating state such as the engine speed and the engine cooling water temperature, and the injector 41 and the spark plug 45 are driven to perform the fuel injection and ignition. Execute. Further, the ECU 51 feeds back the detected oxygen concentration of the exhaust gas to correct the fuel injection amount so that the air-fuel ratio becomes stoichiometric (theoretical air-fuel ratio).

  The ECU 51 can control the intake / exhaust variable valve mechanisms 27 and 28 based on the engine operating state. That is, when the temperature is low, the engine is started, the engine is idle, or the load is light, the exhaust gas blows back to the intake port 19 or the combustion chamber 18 by eliminating the overlap between the exhaust valve 22 closing timing and the intake valve 21 opening timing. Reduce the amount to enable stable combustion and improved fuel efficiency. Further, at the time of medium load, by increasing the overlap, the internal EGR rate is increased to improve the exhaust gas purification efficiency, and the pumping loss is reduced to improve the fuel consumption. Further, at the time of high-load low-medium rotation, the closing timing of the intake valve 21 is advanced, thereby reducing the amount of intake air that blows back to the intake port 19 and improving the volume efficiency. At the time of high load and high rotation, the closing timing of the intake valve 21 is retarded in accordance with the rotation speed, so that the timing is adjusted to the inertial force of the intake air and the volume efficiency is improved.

  Further, in this embodiment, the ECU 51 performs oil dilution suppression control in order to reduce oil dilution and the amount of PM generated (mass and number of particles) when a predetermined condition is satisfied during warm-up operation after cold start. Execute. In this oil dilution suppression control, the exhaust variable valve mechanism 28 is controlled so that the closing timing of the exhaust valve 22 is set to the middle of the intake stroke, and part or all of the required fuel injection amount is from the beginning of the intake stroke until the exhaust valve 22 is closed. In the meantime, the oil is injected into the injector 41 to prevent oil dilution and PM generation.

  In the engine 10 configured as described above, when the piston 14 descends in the cylinder bore 13, air is sucked into the combustion chamber 18 through the intake port 19 (intake stroke), and the piston 14 falls under the intake stroke. The air is compressed by moving up in the cylinder bore 13 through the dead center (compression stroke). At this time, fuel is injected into the combustion chamber 18 from the injector 41 in the intake stroke or compression stroke, and this fuel and air mix to form an air-fuel mixture. When the piston 14 approaches the top dead center of the compression stroke, the air-fuel mixture is ignited by the spark plug 45, the air-fuel mixture burns, and the piston 14 is lowered by the combustion pressure (expansion stroke). The air-fuel mixture after combustion is discharged as exhaust gas through the exhaust port 20 when the piston 14 rises again toward the top dead center of the intake stroke via the expansion stroke bottom dead center (exhaust stroke). The reciprocating motion of the piston 14 in the cylinder bore 13 is transmitted to the crankshaft 16 through the connecting rod 17, where it is converted into a rotational motion and taken out as an output. When 16 further rotates due to inertial force, the cylinder bore 13 reciprocates as the crankshaft 16 rotates. By rotating the crankshaft 16 twice, the piston 14 reciprocates the cylinder bore 13 twice, during which a series of four strokes including an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke is performed, and once in the combustion chamber 18. Explosion takes place.

  Next, with reference to FIGS. 2 to 7, the control during the warm-up operation after the cold start of the engine 10 by the ECU 51 will be described in detail. FIG. 2 is a schematic diagram for explaining the effect of the oil dilution suppression control of this embodiment.

  As described above, when the in-cylinder direct injection engine is cold started, the flow in the cylinder is weak, so the amount of fuel adhering to the cylinder wall tends to increase, and some of the fuel droplets adhering to the cylinder wall vaporize. If it is mixed into the engine oil without causing any trouble, there is a risk of causing a harmful effect such as so-called oil dilution. In this case, a method of suppressing oil dilution by fuel by setting the fuel injection timing to the initial stage of the intake stroke where the fuel does not adhere to the cylinder wall surface can be considered.However, if the fuel injection timing is set to the initial stage of the intake stroke, Since fuel adheres, there is a problem of causing smoke and PM generation. Therefore, in this embodiment, when oil dilution suppression control is performed during the warm-up operation after the engine is started, the closing timing of the exhaust valve 22 of the exhaust variable valve mechanism 28 is set to the middle of the intake stroke, and one of the required fuel injection amounts is set. By injecting part or all from the injector 41 from the beginning of the intake stroke until the exhaust valve 22 is closed, oil dilution and the amount of PM generated (PM mass and number of PM particles) are reduced.

  As shown in FIG. 2, when the closing timing of the exhaust valve 22 is set to the middle stage of the intake stroke and a part or all of the required fuel injection amount is injected from the beginning of the intake stroke until the exhaust valve 22 is closed, the injector 41 causes the combustion chamber 18 to The fuel 70 injected into the interior of the piston 70 and the cylinder bore 13 of the piston 14 are caused by the flow of the exhaust gas flowing back from the exhaust valve 22 and the temperature rise, and the fuel 70 is accelerated and the penetration force is reduced. Adhesion to the (cylinder wall surface) can be suppressed, and it is possible to achieve both oil dilution and reduction in PM generation.

  FIG. 3 is a flowchart for explaining the control by the ECU 51 during the warm-up operation after the cold start of the engine 10. With reference to FIG. 3, the control by the ECU 51 during the warm-up operation after the cold start of the engine 10 will be described. In the figure, first, the ECU 51 takes in the oil temperature detected by the oil temperature sensor 63 (step S1), and then detects or estimates the oil dilution rate wt% (step S2).

  Here, the oil dilution rate wt% is a value obtained by dividing the weight of the fuel contained in the engine oil by the weight of the engine oil, and can be represented by, for example, the following formula (1). As a method for detecting or estimating the oil dilution rate wt%, a known method can be used. For example, a method disclosed in Japanese Patent Application Laid-Open No. 2006-183563 can be used, and detailed description thereof is omitted here.

  Oil dilution ratio = (weight of fuel supplied to engine oil−weight of fuel evaporated from engine oil) / weight of engine oil (1)

  Based on the calculated oil dilution rate and the detected oil temperature, the ECU 51 refers to the oil dilution suppression control determination map and determines whether to execute oil dilution suppression control (step S3). FIG. 4 is a diagram illustrating an example of an oil dilution suppression control determination map. As shown in the figure, in the oil dilution suppression control determination map, a suitable oil dilution suppression control execution region A1 obtained by experiment or simulation is registered with the oil temperature and the oil dilution rate% as variables. The oil dilution suppression control execution region A1 is a region where the oil temperature <the specified temperature T2 (before engine warm-up) and the oil dilution rate is equal to or higher than a reference value. The ECU 51 refers to the oil dilution suppression control determination map based on the current oil dilution rate and oil temperature, and determines whether or not the oil dilution suppression control execution region A1 exists.

  When the oil dilution suppression control is not executed (“No” in step S3), the ECU 51 executes normal operation control (step S4) and injects fuel from the injector 41 at the normal valve timing and fuel injection timing (step S4). Step S5). In normal operation control, after the exhaust valve 22 is closed, fuel injection is performed twice in the intake stroke.

  On the other hand, when executing the oil dilution suppression control (“Yes” in step S3), the ECU 51 refers to the oil temperature / oil dilution rate / intake stroke injection amount calculation map and calculates the calculated oil dilution rate wt (% ) And the detected oil temperature (° C.), the fuel injection amount X (%) in the intake stroke is determined (step S6).

  FIG. 5 is a diagram showing an example of an oil temperature / oil dilution rate / intake stroke injection amount map. As shown in the figure, the oil temperature / oil dilution rate / intake stroke injection amount map is a variable of the oil temperature and oil dilution rate as variables, and the second fuel injection amount X ( %) Is registered stepwise between 50% and 100%, and the second fuel injection amount X (%) in the intake stroke is increased as the oil dilution ratio increases. The ECU 51 refers to the oil temperature / oil dilution rate / intake stroke injection amount map, and the second fuel in the intake stroke of the oil temperature / oil dilution rate / intake stroke injection amount map corresponding to the current oil dilution rate and oil temperature. An injection amount X (%) is calculated.

  Next, the ECU 51 refers to the oil temperature / oil dilution rate / exhaust valve closing timing (EVC) map and determines the exhaust valve closing timing corresponding to the calculated oil dilution rate and the detected oil temperature (step S7). . FIG. 6 is a diagram showing an example of an oil temperature / oil dilution rate / exhaust valve closing timing map. As shown in the figure, the oil temperature / oil dilution rate / exhaust valve closing timing map shows that the preferable exhaust valve closing timing obtained by experiment or simulation using the oil temperature and oil dilution rate as variables is ATDC = 60 ° to It is registered in steps between 90 °, and the exhaust valve closing timing is retarded as compared with ATDC = 3 ° of the exhaust valve closing timing (ECV) in the normal operation region, and the oil dilution rate becomes higher as the oil dilution rate becomes higher. The retard amount of the closing timing of the exhaust valve 22 is increased.

  The ECU 51 causes the injector 41 to perform fuel injection at the calculated exhaust valve closing timing and fuel injection amount (step S5). That is, with the closing timing of the exhaust valve 22 set to the middle of the intake stroke, fuel split injection is performed until the exhaust valve 22 is closed in the intake stroke, and in the first fuel injection, the required fuel injection amount is 100-X. (%) Of fuel is injected, and in the second fuel injection, X (%) of the required fuel injection amount is injected.

  FIG. 7 is a diagram illustrating an example of a timing chart of the exhaust valve opening / closing timing and the fuel injection timing during normal operation control and oil dilution suppression control. In the figure, (A) shows normal operation control, and (B) shows oil dilution suppression control, and shows a case where fuel injection is performed twice. During normal operation control, as shown in (A), after the exhaust valve 22 is closed, fuel is injected twice in the intake process. For example, the fuel injection amount in each normal operation control can be 50% of the required fuel injection amount. On the other hand, in the case of oil dilution suppression control, as shown in (B), the closing timing of the exhaust valve 22 is retarded from that during normal operation control to the middle stage of the intake stroke. In the intake process, before the exhaust valve 22 is closed, the first fuel injection of 100-X (%) of the required fuel injection amount and the second fuel injection of X (%) of the required fuel injection amount are performed.

  As described above, according to this embodiment, in the direct injection internal combustion engine, the ECU 51 detects the oil dilution rate detected by the oil temperature sensor 63 or the oil temperature detected during the warm-up operation after starting the engine and the oil temperature detected by the oil temperature sensor 63. Is determined whether or not oil dilution suppression control is necessary. If it is determined that oil dilution suppression control is necessary, oil dilution suppression control is executed and the exhaust variable valve mechanism 28 closes the exhaust valve 22. The timing is set to the middle of the intake stroke, and part or all of the required fuel injection amount is injected into the injector 41 from the beginning of the intake stroke until the exhaust valve 22 is closed. In addition, the amount of PM generated can be reduced.

  Further, according to the present embodiment, in the oil dilution suppression control, fuel split injection is performed, and the second fuel injection is performed until the exhaust valve 22 is closed in the intake stroke. It is possible to achieve a balance between oil dilution and PM generation during machine operation.

  Further, according to the present embodiment, X (%) of the required fuel injection amount is injected in the second fuel injection of the oil dilution suppression control, and 100-X (the required fuel injection amount in the first fuel injection). %) And the injection amount X (%) is increased as the oil dilution rate is higher. Therefore, the degree of oil dilution suppression can be adjusted according to the oil dilution rate.

  Further, according to the present embodiment, in the oil dilution suppression control, the closing timing of the exhaust valve 22 is retarded as the oil dilution rate increases, so the degree of oil dilution suppression is adjusted according to the oil dilution rate. It becomes possible.

  The internal combustion engine according to the above-described embodiment of the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope described in the claims. In the oil dilution suppression control, the exhaust valve 22 may be opened and closed again using an electromagnetic valve or the like in accordance with the fuel injection timing in the intake stroke.

  As described above, the internal combustion engine according to the present invention is suitable for use in various in-cylinder direct injection internal combustion engines that inject fuel directly into a combustion chamber.

It is a schematic block diagram showing the engine which concerns on the Example of this invention. It is a schematic diagram for demonstrating the effect by the engine control at the time of the cold start by a present Example. It is a flowchart for demonstrating the control at the time of warming-up operation after the cold start of the engine by ECU. It is a figure which shows an example of an oil dilution suppression control determination map. It is a figure which shows an example of an oil temperature and an oil dilution rate / intake process injection amount map. It is a figure which shows an example of an oil temperature and an oil dilution rate / exhaust valve closing timing map. It is a figure which shows an example of the timing chart of the exhaust valve opening / closing timing at the time of normal driving | operation control, and oil dilution suppression control, and fuel injection timing.

Explanation of symbols

10 Engine (Internal combustion engine)
13 Cylinder bore 14 Piston 18 Combustion chamber 19 Intake port 20 Exhaust port 21 Intake valve 22 Exhaust valve 27 Intake variable valve mechanism 28 Exhaust variable valve mechanism 41 Injector (fuel injection device)
45 Spark plug 51 ECU (control means, determination means, oil dilution rate calculation means)
58 Water temperature sensor
63 Oil temperature sensor (oil temperature calculation means)

Claims (4)

In an internal combustion engine in which fuel is directly injected into a cylinder by a fuel injection device,
A variable valve mechanism capable of changing at least the opening / closing timing of the exhaust valve;
Oil dilution rate calculating means for detecting or estimating the oil dilution rate of engine oil;
Oil temperature calculating means for detecting or estimating the oil temperature of the engine oil;
Determines whether or not oil dilution suppression control is necessary based on the oil dilution rate detected or estimated by the oil dilution rate calculation means and the oil temperature detected or estimated by the oil temperature calculation means during warm-up operation after engine startup Determination means to perform,
Control means for executing the oil dilution suppression control when the determination means determines that the oil dilution suppression control is necessary;
With
In the oil dilution suppression control, the closing timing of the exhaust valve of the variable valve mechanism is set to the middle of the intake stroke, and part or all of the required fuel injection amount is from the initial intake stroke to the closing of the exhaust valve. An internal combustion engine characterized by being injected by a fuel injection device.   2. The internal combustion engine according to claim 1, wherein in the oil dilution suppression control, the fuel is dividedly injected, and fuel is injected twice during the intake stroke until the exhaust valve is closed.   In the second fuel injection, X (%) of the required fuel injection amount is injected, and in the first fuel injection, 100-X (%) of the required fuel injection amount is injected, and the X (%) is used as the oil. 3. The internal combustion engine according to claim 2, wherein the internal combustion engine is increased as the dilution rate is higher.   4. The internal combustion engine according to claim 1, wherein, in the oil dilution suppression control, the closing timing of the exhaust valve is retarded as the oil dilution rate increases. 5.

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